Electronic display panels, either of the cathode ray tube (CRT) type or of the liquid crystal display (LCD) type, have been widely used in recent years for various electronic display applications. The recent advancement in home computers or personal computers has made such applications even more popular. In the computer display applications, it is sometimes desirable to add the touch screen feature to the display panel such that an interaction between the computer user and the computer can be executed directly without the use of a keyboard or a mouse. Such convenience has further strengthened the even broader usage.
A touch screen, or a touch sensitive display panel typically involves a cathode ray tube monitor and a transparent touch-sensitive overlay that is attached to the front face of the monitor. The display panel may be part of a system including a computer and an internal/external video source for feeding electronic information into the computer. A software program is prepared for execution of the touch screen command of the computer user; for instance, the program determines the response of the system when the display screen is touched at a particular X-Y coordinates. The touch screen action of the computer user executes any desired actions for retrieving or displaying information on a display panel.
Conventionally, touch screen display panels are fabricated by adding a touch sensitive overlay, which is constructed of either a resistor type or a capacitor type. For instance, a series of resistors or capacitors in the form of conductors can be fabricated in layers in the overlay such that, when a particular point of the overlay surface is touched, the two spaced-apart resistors or capacitors are shorted together and thus producing a specific resistance or capacitance value indicative of the X-Y coordinates of the touched location on the overlay.
In recent years, piezoelectric type pressure-sensitive transducers have been used in touch screen display panel applications. For instance, U.S. Pat. No. 4,675,569 discloses such an application for CRTs 25, shown in FIG. 1.
In the CRT application of the piezoelectric transducers, a touch screen is constructed and attached to a conventional CRT 10 that has a front surface 12 and a housing 14. A metal band 16 is secured to the housing 14, including mounting ears 18 at each of the four corners of the housing. The ears 18 are used to bolt the CRT tube to a chassis that has inwardly extending tabs 20. The touch screen assembly 22 is therefore secured to the CRT 10 by the chassis tabs 20, and the CRT ears 18. The touch screen assembly 22 further includes a frame 24, which has integral cones 26 that extend toward the CRT 10 and at each of the four corners of the frame. The cones 26 have openings, which are aligned with the openings in the CRT ears 18, and chassis tabs 20 with deformable grommets 28 mounted in the opening of the cones. A rubber gasket 30 is seated against the surface of the frame 24 and held in place by a number of integral pins 32 that fit into matching openings 34 in the frame 24.
A rigid transparent plate 36, which is made of glass, is seated against the rubber gasket 30 in a recess on the surface of frame 24. The glass plate 36 functions as a push plate for a user to tap or touch during operation of the touch screen panel. The curvature of the plate 36 and the curvature of the plate 24 generally match the curvature of the front surface 12 of the CRT 10. Force-sensitive or piezoelectric transducers 38 are attached to one surface of the plate 36 by using tabs 40 that have layers of adhesive on both surfaces. Each of the transducers 38 is coupled to a connector by a conductor such as a wire 42. The electrical current produced by each of the piezoelectric transducers 38 is proportional to the force exerted of the transducer. The touch screen assembly further requires a flexible, dust impervious frame member 45, which is attached to the parameter of the push plate 36 by adhesive means. The frame member 45 provides a dust seal between the CRT front surface 12 and the push plate 36 to minimize the amount of dust that is attracted to the front surface 12 during operation. The touch screen mounting assembly is further secured to the CRT ears 18 and chassis tabs 20 by means of studs 44 that have threads at both ends. The studs extend through the openings in the cones 26 and are encircled by coil springs 46 which are held in place by fastening elements or washer nuts 48.
The touch screen assembly for the CRT application shown above required the necessary member of the rigid transparent plate, or the glass plate 36 to transfer the touch pressure from the user to the force-sensitive transducers. The use of such glass plate that covers the front surface of the display panel affects the brightness and color of the panel. The negative effect on the brightness and color becomes more severe when the display panel is a liquid crystal display, instead of a CRT display, due to the fact that the LCD display inherently has a lower brightness and color not as vivid. The touch screen mounting assembly disclosed by U.S. Pat. No. 4,675,569 is therefore not adequate for use on a LCD application.
It is therefore an object of the present invention to provide a touch screen mounting assembly for a LCD panel that does not have the drawbacks or shortcomings of the conventional mounting assemblies.
It is another object of the present invention to provide a touch screen mounting assembly for a LCD panel that does not require the use of an additional rigid transparent panel mounted in front of the LCD panel.
It is a further object of the present invention to provide a touch screen mounting assembly for a LCD panel wherein a plurality of pressure-sensitive transducers is mounted directly to the frame of a backlight panel.
It is another further object of the present invention to provide a touch screen mounting assembly for a LCD panel that utilizes a plurality of pressure-sensitive transducers mounted sandwiched between a backlight panel and a liquid crystal display panel.
It is still another object of the present invention to provide a touch screen mounting assembly for a LCD panel by utilizing a plurality of attachment means for mounting a top frame to a bottom frame with a backlight panel, a liquid crystal display panel and a plurality of pressure-sensitive transducers sandwiched therein between.
It is yet another object of the present invention to provide a method for fabricating a touch screen mounting assembly for use on a LCD panel by utilizing a plurality of attachment means incorporating compressible springs and a plurality of pressure-sensitive transducers such as piezoelectric sensors.